Gas lift valve

ABSTRACT

There has always been a never ending pursuit of greater efficiency in gas lift operations by which the nearest possible, to optimum amount of gas and of gas pressure energy, is used to lift liquid from wells. One important factor in the never ending pursuit of this goal, is effective control of &#39;&#39;&#39;&#39;valve spread,&#39;&#39;&#39;&#39; and convenience of modification of valve spread to accommodate system parameters. This invention is an improvement in gas lift valves, which improvement relates to valve spread in valves embodying &#39;&#39;&#39;&#39;lost motion&#39;&#39;&#39;&#39; features, to ease and convenience of modification the valve opening and/or valve closing responses, by the combination of &#39;&#39;&#39;&#39;lost motion&#39;&#39;&#39;&#39; valve features with a certain detent means operating between the valve chassis or housing and a valve actuator or carrier.

United States Patent [15] 3,654,949 [451 Apr. 11,1972

Primary Examiner-Alan Cohan Att0rneyAm0ld, White & Durkee, Tom Arnold, Bill Durkee, Robert A. White, Frank S. Vaden, 11], Louis T. Pirkey and John F. Lynch ABSTRACT There has always been a never ending pursuit of greater efiiciency in gas lift operations by which the nearest possible, to optimum amount of gas and of gas pressure energy, is used to lift liquid from wells. One important factor in the never ending pursuit of this goal, is effective control of valve spread," and convenience of modification of valve spread to accommodate system parameters. This invention is an improvement in gas lift valves, which improvement relates to valve spread in valves embodying lost motion" features, to ease and convenience of modification the valve opening and/or valve closing responses, by the combination of lost motion valve features with a certain detent means operating between the valve chassis or housing and a valve actuator or carrier.

16 Claims, 17 Drawing Figures PATENTEDAPR 1 1 I972 SHEEI 3 [IF 7 IN VENTOR.

PATENTEDAPR 1 1 m2 SHEET 8 BF 7 [Vere fl Mc/Wurry PATENTEDAPR 1 1 m2 SHEU 7 BF 7 Km y Q NW M m a E GAS LIFT VALVE SUMMARY OF THE INVENTION This invention relates to the production of liquid from wells and more particularly to a system for promoting the production of liquids, for example such as oil, from wells by the introduction of gaseous fluid under pressure. And further in particular, this invention is in the nature of improvements upon valves characterized by my US. Pat. No. 3,175,514 issued Mar. 30, 1965, the improvements relating to control of valve opening and control of valve closing.

THE ART TO WHICH THE INVENTION RELATES In the gas-lift art the gas may be a hydrocarbon gas, air or any other gas, though for safety reasons it is preferably one that will not support combustion in context of its use. Accordingly, in this specification gas should be understood to mean gaseous type fluids generally, and not just hydrocarbon gas or any other particular gas.

It commonly occurs that wells, such as oil wells, are found to have sufficient producing formation pressure to cause liquid to flow into the lower reaches of the well bore, but have insufficient natural formation pressure for economic movement, or for any movement, of liquid all the way from the producing formation to the ground surface. In the operation of such wells, it is customary to utilize a gas lift system (see FIG. 1) by which gas under pressure may be introduced into a gas injection conduit (usually the annulus A between the well casing C and the production tubing or string T disposed therein), then communicated to the producing conduit (usually the internal bore 20 of the production tubing or string within the well) to cause an upflow of oil and gas in the tubing.

The gas lift valve assemblies V used in this method of operation are commonly spaced at intervals along the production conduit and adjusted so that a selected valve is opened and closed upon the occurrence of approximately predetermined pressure conditions in the tubing and/or annulus so that gas is permitted to enter the tubing only at a location and under pressure conditions to cause an outflow of oil which outflow is at least tolerably efficient as a function of gas used.

In oil well operations wherein the present invention has its most common application, the practice is to introduce a mass of gas in a single bubble into the production tubing T, the gas bubble to act as a piston lifting a slug of oil much as a bubble of steam in a coffee percolator lifts water upward in the percolator's tube. When such a slug of oil has been produced, the pressure in the production tubing T and hence upon the producing formation in the earth is reduced by the loss of hydrostatic head of the oil produced, and now oil flows into the production tubing T in response to producing formation pressure. When an appropriate head of oil has moved into the tubing above the operating gas lift valve, another bubble of gas is injected into the production tubing to produce the next slug of oil.

In one common application of the general production method, gas lift valves are provided with mechanism by which the valves are normally held closed, and are opened when the pressure relationships reach approximately predetermined values. Such valves are often constructed with a pressure chamber in communication with a pressure responsive device such as a diaphragm (Walton U.S. Pat. No. Re. 24,015), bourdon tube (Archer U.S. Pat. No. 1,687,317), piston (Walton U.S. Pat. No. 3,213,806), flexible walled cylinder (Cummings U.S. Pat. No. 2,642,889), or more commonly a bellows (Archer U.S. Pat. No. l,780,808; Traylor U.S. Pat. No. 1,902,296; Zaba U.S. Pat. No. 2,633,086).

The pressure chamber may contain at least significant gas under pressure and the pressure responsive device may be positioned to exert a closing force upon the valve and to be acted upon by the pressure in the valve environs to open the valve when the environmental pressure reaches a predetermined level. Depending upon choice of system design, the gas injection conduit pressure and/or the producing conduit pressure may be concurrent or essentially independent factors in the valve's opening or closing.

Economic operation of gas lift systems is attended by the ever-present problem of timing the opening and closing of the gas lift valves in carefully regulated pattern in accordance with the amount of oil which is available to be removed from the well and in accordance with the amount of gas-pressure energy that'is available to move that oil. Large volumes of gas at high pressure may be wasted either in flowing smaller quantities of oil than could be efficiently obtained or in allowing the gas to enter the tubing when there is no oil to be lifted by the gas or when there is inadequate gas energy to lift the volume of oil that exists above the working valve.

Further, the operation is highly ineflicient if the volume and pressure of gas injected into the production tubing is insuffi cient for rapidly raising the quantity of oil in the tubing the full distance from the gas lift valve to the ground surface. If the oil is moved slowly, much of the slug of oil slips back down the producing conduit and is not delivered at the well head. In gas lift valve mechanism of common design the opening and closing movements of the valve are often relatively slow, so that at the beginning of the opening movement and/or just prior to the closing of the valve, the valve is in a partially opened or cracked condition which results in throttling and/or chatter, and the rapid cutting or wearing away of the valve seat and other parts. One of the objects of my U.S. Pat. No. 3,175,514 was the elimination of this difficulty in a highly preferred manner.

Even with that problem eliminated by the manner of that patent, certain other preferred functions are not readily obtained by any of the structures heretofore used.

Consider for example, the valve design characteristic known as spread." Assume formation pressure has caused oil to rise in the production tubing T a reasonable number of feet above a given gas lift valve to create a tubing back pressure of perhaps 420 psi on the downstream side of the valve. And assume gas is being injected into the annulus A. Assume that the dimensions of the bellows 39, valve opening 31, and the like are such that an annulus pressure of about 625 p.s.i. (pounds per square inch) will collapse the bellows, with aid of 420 p.s.i. back pressure to cause the valve to open, pennitting gas then to flow from the annulus A through the valve into the production tubing T to produce the slug of oil above the valve.

As soon as the valve opens, the annulus pressure commences to be reduced by the flow of gas from the annulus A into the production tubing T and the pressure in the bellows 39 then tends to close the valve again, perhaps long before enough gas has passed for efficient production of the particular slug of oil in the production tubing. The spread between valve opening pressures and valve closing pressures and/or the spread in time between valve opening and valve closing is one of the most critical design criteria for efficient gas lift operations.

The design of my U.S. Pat. No. 3,175,514 conveniently affords a natural valve spread that is appropriate for many system applications, but those working in the art are still seeking improved means for and methods of enlargement of and control of valve spread, for example to assure that the valve does not open until suflicient gas is available to lift the slug of oil and to assure that the valve does not close until adequate gas to deliver the oil at the well head has passed from the annulus into the production tubing.

In accordance with this invention the desired movement is accomplished in structures as disclosed in my U.S. Pat. No. 3,175,514 by affording either a delayed opening of the valve, a delayed closing of the valve, or both, the pressure responsiveness of the delay being easily engineered for highly efficient operation and convenience of change in the field, in each different well installation.

Other improvements of function and of facility of design will be apparent from the following description in conjunction with the drawings.

FIG. 1 is a fragmentary diagrammatic view of a singly completed well illustrating typical arrangement of gas lift apparatus in a well.

FIG. 2 is a fragmentary side elevational view, partly broken away and partly in cross section, illustrating a gas lift valve utilizing one embodiment of the invention and showing the details of structure and arrangement of its parts and one of the several manners in which the valve may be connected to production tubing for use in a gas lift system.

FIGS. 3 and 4 constitute the upper and lower portions of the valve embodiment shown in FIG. 2, illustrating further details of constructions of the valve.

FIGS. 5,6 and 7 all show a portion of the valve of FIGS. 2 and 3-4 in fragmentary vertical cross-section, FIG. 5 showing the valve in cocked closed position, and FIG. 7 showing the valve in open position.

FIGS. 8, 9 and also in fragmentary vertical cross-section, illustrate a portion of a different valve embodiment, FIG. 8 illustrating the valve in uncocked closed position, FIG. 9 illustrating the valve in its closure-delayed position, and FIG. 10 illustrating the valve in full open position.

FIGS. ll, 12 and 13 illustrate still another valve embodiment, again in vertical fragmentary cross-section, FIG. 11 illustrating the valve in full closed position, FIG. 12 illustrating the valve in cocked and opening-delayed position, and FIG. 13 illustrating the valve in full open position.

FIG. 14 is a chart illustrative of the spread characteristics of valves, the chart being not to precise scale but being adequate for illustration of principle.

FIGS. l5, l6 and 17 illustrate a valve in different positions, with an alternative embodiment of one preferred detent mechanism, wherein the detent spring is disposed axially of the valve and wherein the detent shoulders are at different angles whereby the spread added on valve opening can be rendered different from the spread added on closing.

While the invention may be used in conjunction with various of the gas lift systems disclosed in patents and other literature, FIGS. 1 and 2 illustrate an example of a system wherein the invention is useful. There you will see schematically a well bore hole in the earth, which bore hole is lined with a casing C extending somewhat above the surface of the ground at G. Within the bore hole and casing C is located production tubing or tubing string" T extending from the proximity of the oil producing formation at its lower end to permit the inflow of oil from the producing formation, and connected at its upper end to a suitable outflow line L through which the oil is conducted to any desired location.

In many installations the annulus A between the production tubing T and casing C is blocked at a location above the oil producing formation by a conventional packer P.

The casing C is closed at its upper end by a casing head structure of conventional design. As illustrated schematically the annulus between the casing C and the production tubing T is in communication with an appropriate source S of gas under pressure, such as a high pressure line, a pressure tank or a compressor. Conveniently the gas source S may be connected to the annulus A through a choke K and/or some other means for regulating the inflow of gas into the annulus A, such as a regulator as disclosed in King U.S. Pat. No. 2,339,487.

The annulus A above the packer P constitutes both the gas injection conduit in the system as illustrated, and also a gas reservoir or pressure chamber surrounding the production tubing T.

For the purpose of introducing gas under pressure from the annulus A into the tubing T at various levels, a number of gas lift valve assemblies V are connected into the tubing T at longitudinally spaced locations, these valves being adjusted to open and close upon the occurrence of predetermined pressure conditions within the tubing T and/or the annulus A.

The arrangementmay be reversed from that illustrated in FIG. 1, such that the production is through the annulus A and the gas injection is through the tubing T. In such a reverse installation the tubing would become the gas injection conduit and the annulus the producing conduit.

Inn

Convenient means may be provided for attaching the valve assemblies V to the string to production tubing T. Such means may take the form taught in Howard at al. U.S. Pat. No. 2,664,162 and McGowen et al. U.S. Pat. No. 2,679,903 or any one of a number of other forms illustrated in the art. In the embodiment here illustrated in FIG. 2, the string or production tubing T includes short sections or subs" 15 connected by threads (not shown) at each end to the tubing below and above the section. Each such tubular section 15 has longitudinally spaced, laterally projecting, upper and lower lugs 16 and 17 secured thereon, into which the valve assembly V is fitted.

The upper lug 16 has a central, longitudinal, counter bore 18 and is provided with openings 19 providing communication between the counter bore 18 and the interior 20 of the production tubing section 15.

In some installations, means may be provided for blocking all substantial flow from the production conduit 20 (inside the tubing section 15 and tubing T), back toward the gas injection conduit A, while permitting flow in the gas lift valves normal downstream direction toward the production conduit 20. Such means may take the form of a check valve assembly 21, the illustrated embodiment comprising a seat 22, a check valve member 23 and a non-seating abutment 24, all within the check valve housing 25, having flow ports 26 around the abutment 24.

The valve assembly V is mounted to afford fluid communication when the valve V is open, between the gas injection conduit or annulus A, through the valve assembly V, through the check valve assembly 21, the counter bore 18 and openings 19 to the production conduit 20.

One form of valve assembly V is illustrated in FIGS. 3-4. The chassis of this valve assembly can be said to comprise a threaded mounting plug 30, having a valve seat 31 therein; an upper housing 32 of generally cylindrical form secured to said mounting plug 30; a central mandrel 33 secured to said upper housing 32; a dome 34 secured to said central mandrel 33; and dome closure means 35 for permitting gas or gas plus liquid to be inserted into the dome and then securely sealed against leakage.

Within the housing 32 are main flow openings 36, in the embodiment shown being of relatively large size to present essen tially no resistance to fluid flow by comparison with the restriction of flow through the valve seat 31 and flow path 37. Normal downstream gas flow is then seen to be through the main flow openings 36, through the valve seat 31 when it is open, and then through outlet port and flow path 37 within the plug 30, through the check valve assembly 21 (FIG. 2), counter bore 18 and openings 19 into the production conduit 20.

The valve assembly V is of course provided with a valve closure member 38 adapted to close on the valve seat 31, or to be removed therefrom in order to open the valve assembly for fluid flow therethrough.

In accordance with this invention a pressure responsive means, is mounted in the valve assembly V. Conveniently this pressure responsive means may take the form of a bellows 39 illustrated in FIG. 3, the bellows 39 being sealed at one end to the central mandrel 33, and sealed to a movable bellows head 40 at its other end. The central mandrel 33 has a cylindrical opening therethrough, by which fluid in the pressure chamber or dome 34 and the bellows 39 may, in the illustrated embodiment, remain at all times in communication.

In order that the bellows 39 may be freely exposed to fluid pressures in the gas injection conduit A, it may be convenient to provide additional ports 41 in the upper housing 32. The pressure in dome 34 operates on one side of the bellows 39; the gas injection conduit pressure operates on the other side of the bellows 39. It is apparent that the bellows expands and contracts, in accordance with the pressure differential between the dome 34 and the gas injection conduit annulus A, the response to this pressure differential being modified by any spring forces, gravity forces or other forces that may also be applied. The bellows expansion and contraction moves the bellows head 40 toward the valve seat 31 as the bellows expands in response to relatively low gas injection conduit pressure and away from that valve seat as the bellows contracts in response to relatively high gas injection conduit pressure.

If desired, means may be provided for limiting the bellows head 40 in its movement toward and away from the valve seat 31, to what may be termed first and second extreme positions. As illustrated such means may take the form of a rod 42 mounted in the bellows head 40 and extending through the central mandrel 33, such rod 42 carrying a pin 43 adapted to engage the end 44 of the central mandrel 33 to prevent the bellows 39 from becoming over extended (as for example, when the valve is partly disassembled). This defines the valveclosed limit position for bellows head 40. And the rod 42 may be dimensioned to abut the dome closure means at the surface 29 so as to limit the bellows collapse and limit movement of the bellows head in the direction away from the valve seat 31. This defines the valve-open limit position.

Means are provided by which the movements of the bellows head 40 are applied in a preferred manner to influence and/or control the movements of the valve closure member 38. The bellows head 40 is really a part of the actuator for the valve closure member 38, for this head and its appendages must actuate the valve closure member at least in part. In the embodiment illustrated, the valve actuator takes the form of the composite of the bellows head 40 and an integral valve carrier 45. The valve carrier 45 may be of a cylindrical, cage finger or other form, housing therein the shaft or stem portion 38A and the head portion 38B of the valve closure member 38.

Some form of means or facility is provided, to bias and urge the valve closure member 38, in a direction away from the valve seat 31, while permitting it also to move relative to the valve carrier 45 in a direction toward the valve seat 31. If the valve is oriented upside down from the orientation shown, the valve member 38 may be so weighted that gravity on the valve closure member 38 may be that facility, for gravity then will function as a bias means. Or the bias means may take the form of perhaps a magnetic force or a spring operative between the housing 32 and the valve closure 38. But in the illustrated embodiment it takes the form of a valve spring 46 compressed between a downward facing abutment surface 47 of the valve carrier 45 and an upward facing abutment surface 48 of the valve closure member head 38B.

Means are provided to limit the movement of the valve closure member 38 in the direction away from seat 31, and to force said valve closure member to the proximity of seat 31 upon movement of the valve actuator to near to the valve-seat limit position of its movement. In the embodiment disclosed this takes the form of a toward-the-valve-seat-acting (in the drawing, upward acting) abutment surface 49 of the valve carrier 45. This abutment surface 49 is adapted to abuttingly engage the valve closure member head 388.

In accordance with this invention, means may also be provided by which the valve closure member 38 is forced off its seat 31 upon the event of collapse of the bellows 39 and movement of the valve actuator to the near-full open position of its movement. For example, the valve spring 46 may be so dimensioned that it is fully collapsed and becomes a positive push member when the bellows 39 has collapsed half way. Or as in the embodiment illustrated, internal of the valve carrier 45 there may be provided an intermediate abutment shoulder 50,

positioned such that after a predetermined amount of OPERATION OF TYPICAL SYSTEM In a typical operation of the parts thus far described, a string of tubing T with check valve assemblies 21 and gas lift valve assemblies V mounted thereon, is run into a well bore inside casing C, which casing is perchance partly loaded with kill fluid.

The domes 34 of the gas lift valves are pre-charged with preselected pressures, let us assume an uppermost valve at 610 psi, a middle valve at 600 p.s.i., and a lowermost valve at 590 p.s.i.

As the tubing string T is run into the well, a head of heavy kill fluid is found above all three of the valves in our hypothetical story.

In accordance with this invention, the cross sectional area of the valve seat 31 is smaller than the cross sectional area of the bellows 39, such that at high annulus pressures there is more opening force by bellows collapse than closing force upon the valve closure member 38, and full bellows collapse causes the intermediate abutment shoulder 50 to engage the valve closure head abutment surface 48 to open the gas lift valve.

The hydrostatic head of kill fluid plus gas injection pressure in the gas injection conduit A, may be sufficiently high that all of the gas lift valves are opened. Gas passes down the injection conduit A pushing kill fluid ahead of it through one or all valves to blow the kill fluid up and out of the production tubing T.

Then the pressure is bled down such that each of the gas lift valves in turn closes in response to its bellows expansion against decreasing pressure.

The oil producing sands natural pressure, which presumably is inadequate to produce oil against the hydrostatic pressure of the kill fluid, is able to produce oil into the production conduit 20, now that this conduit is freed of that kill fluid pressure load. Oil flows until it is some feet above, shall we say, the 600 p.s.i. valve. As this occurs, gas is injected into the gas injection conduit 20 until the pressure exceeds 600 p.s.i. at the level of the subject valve, thereby commencing to collapse the bellows of the valve and compress or cock the spring 46 by downward movement of the valve carrier as the bellows collapses.

In accordance with one common usage of the invention, the valve opening forces are partly in response to the bellows collapse force transmitted either directly through abutments 48 and 50 or indirectly through the valve spring 46, and partly in response to build-up of an appropriate head of oil in the production conduit 20-a head which produces pressure communicated to the downstream side of the gas lift valve.

Ifthere is no check valve 21 in the installation, this communication is readily apparent; but even when there is a check valve 21, this communication can be depended upon in normal gas lift operation because of slight weapage of one or the other of the gas lift or check valve.

Gas passing through the valve assembly V into the production conduit 20, pushes the liquid therein, whether it be kill fluid, water or oil, to the surface for output through output line L. As the slug of liquid rises, gas in the gas injection conduit, annulus A, is dissipated through the gas lift valve V more rapidly than it is replaced through the choke K, and the annulus pressure falls off until it is below the 600 psi within the dome of the open valve. As this occurs, the bellows 39 ex pands, moving the valve carrier 45 and valve closure member 38 toward seat 31, until throttling commences to occur and effective pressure downstream of the valve closure member 38 is reduced to snap the member closed.

The direction of a role of gravity, frictional forces, the mechanical spring force of the bellows and effective spring rate of the compressible gas charge in the dome 34, are readily apparent regardless of the orientation of the valve, and hence these forces can be disregarded for present discussion purposes.

The gas lift valve V being now closed while new gas is continually injected through choke K, the gas injection conduit pressure again rises above the 600 p.s.i. of the bellows charge, again collapsing the bellows 39 and cocking the valve spring 46. The natural pressure within the oil producing formation below the packer P, assuming it is sufficient, is concurrently moving oil into the production tubing T above the level of the valve that functioned on the first cycle.

Eventually, force of the cocked valve spring 46 exceeds the force of the pressure differential across the valve closure member 38; or force derived from bellows collapse transmitted through the spring 46 or through engagement of the abutments 48 and 50 exceeds the force of the pressure differential across the valve closure member 38; and in either event the valve closure member 38 is again snapped open and the new liquid in the production conduit 20 is again pushed upward to outflow line L by gas from the gas injection conduit, annulus A.

When adequate liquid flows from the producing formation against the fluid head in the production conduit 20, to make a satisfactory slug above the 600 p.s.i. valve operated on the first cycle, the 600 p.s.i. valve fails to open because of lack of back pressure on the downstream side of the valve closure member 38. On the other hand, oil nevertheless rises in the production conduit 20 above the lowermost (590 p.s.i.) valve to generate a back pressure upon its valve closure member 38; and rising annulus pressure at the location of the lowermost valve, when it rises on beyond 590 p.s.i. in our example, serves to collapse its bellows and cock the valve spring 46 of the lowermost valve, to afford snap opening and injection of gas through this lowermost valve to produce the slug of oil above As background for an understanding of FIG. 14 and spread, assume for a moment a valve as in FIG. 2, but with the lost motion feature affording movement between the valve member 38 and the valve carrier 45 eliminated. I.e., as sume that the valve closure member 38 is connected directly to the bellows head 40, so as to preclude relative motion between the two.

In one usage of the language of the art, such a valve is said to be a 10 percent valve when the cross sectional area of the valve seat 31 is 10 percent of the effective cross sectional area of the bellows 39. For purposes of explanation we will assume such a 10 percent valve with its dome 34 charged with 600 p.s.i. and we will disregard the lost motion feature, the spring rate of the bellows walls, the spring rate of the compressible gas in the dome 34, friction and weight of the parts, and will look at the function of the valve as depicted in a portion ofFIG. 14.

Since gas injection conduit pressure works on the valve member 38 to urge it onto seat and also works to collapse the bellows 39 to pull the valve member 38 from its seat, the former having an area 10 percent of the latter, the assumed valve opens at a 666 p.s.i. gas injection conduit pressure (point 70 in FIG. 14) assuming zero production tubing back pressure upon the valve member 38.

That this is correct is seen thus: Assume an effective bellows area of one square inch, and hence in the 10 percent valve a valve seat opening of one-tenth square inch. The opening force is 66 p.s.i. (666 p.s.i. less the 600 counter-pressure in the dome 34) times the 1 square inch of bellows, or 66 pounds. This opening force equals the valve closing force of 66 pounds which is derived from 666 p.s.i. on the valve closure member 38, times its effective area of one-tenth square inch.

Once the valve is open, there is no pressure difierential across the valve member 38 tending to close it, so the valve stays open during injection of gas into the production tubing and resultant draw-down of gas injection conduit pressure.

As the gas injection conduit pressure decreases during injection of gas through the valve into the tubing, the bellows 39 expands, theoretically to reach closure when the gas injection conduit pressure reaches 600 p.s.i. (point 71 in FIG. 14). Because of gas throttling near closure, possible valve chatter upon closure of such a valve, friction and other factors, the 600 p.s.i. theoretical closing may not be precisely that in actual practice, but the example serves for explanation of the valve spread function. And in this example, the valve spread is said to be 66 p.s.i.

THE SNAP AC'llNG EMBODIMENT By adding back in the lost motion feature" as in the structure of FIGS. 3-4, using a weak valve spring 46, and structuring the valve to have a very small distance between valve carrier abutment shoulder 50 and valve closure member abutment shoulder 48, the throttling, chatter and certain other problems are solved with a snap action at opening and closing, but without departure from the theory by which we can assume valve opening at 666 p.s.i. and valve closing at 600 p.s.i. in the gas injection conduit with zero back pressure from the production conduit. This then can be termed the snap acting embodiment-an embodiment which holds substantially to the theory under present discussion.

As seen in FIG. 14, with each p.s.i. increase in the back pressure from the production conduit, the valve spread reduces about 11 p.s.i., until at 600 p.s.i. of production conduit pressure (point 72 in FIG. 14) the valves tendency is to open and close at the same injection conduit pressure and hence the valve cannot function to afford lifting of oil.

If oil is to be produced it must rise in the production conduit to produce a back pressure of, for example 100 p.s.i. In this circumstance, the valve opens at about 651 p.s.i. of injection conduit pressure (FIG. 14 point 73), affording a spread of about 51 p.s.i. before the valve closes at 74. The gas injection commensurate with that 55 p.s.i. draw-down in injection conduit pressure must be sufficient for efficiently raising the oil to the surface, however far that may be. The natural spread of the valve at 100 p.s.i. production conduit back pressure is 55 If the build-up of oil-head back pressure in the production conduit is rapid, back pressure may reach 500 p.s.i. before the injection conduit pressure is restored to 611 p.s.i. In such an event the valve opens (75 in FIG. 14) with a bigger oil load. There is available to lift the load only gas equivalent to II p.s.i. of draw-down in injection conduit pressure to point 76. For a long rise to the ground surface, this quantity of gas may be totally inadequate, and the valve may produce oil either very inefficiently or not at all.

Further, in many installations the production conduit is large relative to the gas injection conduit, and the draw-down then becomes rapid and large. In order to get enough gas from the injection conduit into the production conduit, it may be necessary to afford a draw-down of p.s.i. in the injection conduit. Our assumed 10 percent valve simply cannot accomodate that much spread.

In prior practice, it was necessary to build specially designed valves for all different sizes of gas injection conduits wherein draw-down varies from conduit size to conduit size for the same amount of gas delivery. But by the present invention it is feasible to take a stock valve off the shelf and change the spread for any size of gas injection conduit by merely inserting a detent spring 57 of preselected strength. By the use of this invention, there is no need for either a large inventory of valves of different relative sizes between bellows and valve opening, and no need for the alternative of making up every set of valves only on order for each specific job. It is thus seen that:

One object of the present invention is to afford an easy means for adding known and controlled increments of spread to off-the-shelf valves such as a 10 percent valve that may be carried in inventory, by means that are accomplished in literally a couple of minutes either in the factory or the field-- and without the need to re-manufacture the relative areas of the valve seat opening and bellows, or other valve structures.

PRESSURE DIFFERENTIAL CONTROLLED EMBODIMENT In an alternative embodiment of the same basic structure illustrated in FIG. 3-4, the space between the abutment surface 48 and the intermediate abutment shoulder 50, may be increased to a large fraction of the full stroke of the bellows head 40, so that the valve member 38 is not forced off seat by collapse of bellows 39 until the gas injection conduit pressure is raised arbitrarily high to, for example, 800 p.s.i. And with this embodiment the valve spring 46 is selected to be of an intermediate strength to determine the valves responsiveness on opening to the differential between gas injection conduit pressure and production tubing back pressure, at injection pressures in the below 800 p.s.i. range.

Thus, if the system is designed for normal routine operation with a maximum gas injection conduit pressure of about 700 p.s.i., the valve spring 46 is cocked to its design amount by 700 p.s.i. of injection conduit pressure and the valve then waits for oil to flow into the production tubing sufficient to build up a predetermined back pressure such as 420 p.s.i. which, when coupled with the cock-force of valve spring 46, will open the valve. Since the valve, in normal operation, opens in response to the differential in pressure across the valve closure member 38, this embodiment may be termed the pressure differential controlled valve by contrast with the snap acting embodiment discussed above which in normal operation is opened at least partly by direct application of bellows collapse forces through abutments 48 and 50 to the valve closure member.

Such a valve, normally pressure differential controlled, admits to being opened in the absence of production tubing back pressure, by direct application of bellows collapse forces obtainable by merely raising the injection conduit pressure to perhaps 850 p.s.i. whereby the bellows 39 is collapsed to its full limit, engaging abutments 48 and 50 to open the valve.

It sometimes occurs, however, that it is difficult to control precisely from cycle to cycle and day to day the exact level of injection conduit pressure for the normal-operation cocking of the valve spring 46 in this embodiment of the valve. Particularly is this true when multiple production conduits from different producing formations are being operated from a single gas injection conduit.

It follows that one of several problems only imperfectly solved prior to the present invention, is the problem of continuously effecting optimum production efficiency with this valve embodiment, because the cocked-spring force has varied with the variations in the injection conduit pressure whereas optimum efficiency is in some installations better obtained by rendering that cocked-spring force uniform from cycle to cycle.

The problem of inaccuracy and of inconvenience of control of spread, and the problem of nonuniformity of annulus pressure from cycle to cycle causing some cycles to transpire at markedly less than optimum pressure conditions, have been described by examples of the snap acting and the pressure differential controlled embodiments of the valve, but these problems and others not herein discussed exist in both of these and other gas lift systems.

THE IMPROVEMENT The Embodiment of FIGS. 5, 6, 7

Consider then, the improvement exemplified in one embodiment in FIGS. 5, 6, and 7, wherein means are provided for preselected releasable detention of the valve carrier from moving to its full open position and also for detaining the valve carrier from moving to closed position.

In FIGS. 5, 6, and 7 such means takes the form of a recess 55 in the housing 32, adapted to cooperate with a detent member 56 carried in a transverse hole 58 in the valve carrier member 45 and loaded by a detent spring 57 to be urged into the recess 55. While one such detent member 56 with its own spring may suffice, there is peculiar advantage in the use of a single detent spring 57, positioned in a transverse hole 58 within the valve carrier 45 as illustrated, and urging two diametrically opposed detents 56 into substantially identical recesses 55 or into identical portions of a continuous annular recess 55. It is noteworthy here that the detent functions between some portion of the valve chassis (as illustrated, the housing 32) and the valve actuator (as illustrated, the valve carrier 45), and does not function directly with respect to any portion of the valve closure member 38.

An alternative detent arrangement peculiarly useful when space limitations require a very narrow valve, is illustrated in FIGS. 15, 16 and 17. In this embodiment the detent spring 57 is disposed vertically within a vertical recess 59 within the valve carrier 45. The detent spring 57 urges some sort of what we shall call a wedge member 60, into a concurrent engagement with both the detent members 56, such that the single vertical force of the detent spring 57 is applied to urge the detent members 56 to move outwardly with equal force.

If the wedge member 60 is a ball, cone or a three or four sided pyramid, the single wedge member can be caused to transmit a single detent spring force equally to three or four detent members 56 without departure from the scope of this inventive embodiment.

Such a detent arrangement as is seen in FIG. 3, et seq., or in FIG. 15, forces a continued accurate balance of the two detents 56 on opposite sides of the moving valve carrier member 45 even when the detent spring 57 ages and suffers reduction in its force. Separately actuated detents which may develop somewhat different detent forces, tend to cause valve parts to be pushed to one side, or to turn in a vertical plane, causing erratic and unpredictable frictional drag forces to develop; and these in turn contribute to loss of predictable accuracy in the detent function. Thus, while valves within certain of the scope of this invention might be built with other detent arrangements (e.g., with detent springs and detends in the housing and urging detents toward a recess in the valve carrier or bellows head), the particular preferred detent arrangement is believed to be individually patentable as a key part of the combination herein claimed.

In the illustrated embodiment, the abutment shoulders or walls of the recess 55, or at least the functioning portions thereof, are positioned in the housing relative to the detent members 56 in the valve carrier 45, such that the abutment shoulder portions of the recess 55 and detent 56 come into engagement with each other when the valve carrier 45 is in the cocked position prior to engagement of the two abutments 48 and 50i.e., when the valve carrier is removed from its most extreme position near the valve seat and also is removed from its most extreme position away from the valve seat.

Refer now to FIGS. 5, 6 and 7 where the FIG. 3-4 embodiment of the invention is illustrated in three positions. In FIG. 5 the valve is in the normal closed position, the position to be found when pressure within the dome 34 is perhaps higher than the pressure in the adjacent gas injection conduit A, the bellows 39 being extended such that the valve carrier 45 is at the valve seat end of its movement, the valve spring 46 is not cocked, and the valve closure head 38B is abutting the abutment 47 of the valve carrier.

Such a condition may obtain, to use values similar to the previously discussed example, when the pressure in the valve dome 34 is 600 p.s.i., the annulus pressure is 600 p.s.i., and the tubing backpressure is p.s.i. As pressure rises in the gas injection conduit A, for example to 650 p.s.i. the bellows39 collapses sufficiently to move the valve carrier 45 slightly away from the valve seat, thereby to cock the valve spring 46 a desired amount as illustrated in FIG. 6. The valve closure member 38 remains on seat 31 owing to the differential in gas injection conduit pressure over producing conduit pressure which is impressed across that closure member 38.

With the valve carrier 45 in the cocked position of FIG. 6, the detents 56 engage the recess 55, urged there by the predetermined force of the detent spring 57.

Consider now the snap acting embodiment. As the annulus pressure continues to rise past perhaps 654 p.s.i. at which the valve would normally open with 100 p.s.i. back pressure, and even past 666 p.s.i., the valve remains closed because of the detention of the detents 56.

Assume for a moment that the production formation pressure produces oil in the tubing only to a head of 100 p.s.i. back pressure at the valve. And assume that the detention force of the detent spring 57 is preselected to equate to 75 p.s.i. of

change in annulus pressure. The valve is seen to remain closed until the annulus pressure reaches, to read point 78 from the rough charted example of FIG. 14, about 726 p.s.i. The detents 56 then release; bellows 39 collapses further; the abutments 48 and 50 engage and with aid of the tubing back pressure pull the valve closure member 38 oh seat; and the valve opens to the position illustrated in FIG. 7. The 75 p.s.i. of valve-opening spread added by the detent means is represented by the line 80 (the distance between points 73 and 78 in FIG. 14).

Now assume a higher pressure in the producing formation, and that oil continues to rise in the tubing until the tubing back pressure has reached 420 p.s.i. Without the detents the valve would open at the annulus pressure of point 77 in FIG. 14; but with the detent means the bellows-collapse opening force is not transmitted to the valve closure member 38 until the annulus pressure reaches point 81, which by crude chart reading is something near 700 p.s.i. in the FIG. 14 example. At that point, the detents 56 release; abutments 48 and 50 engage; and with 420 p.s.i. tubing back pressure the valve opens.

If either the annulus pressure of about 700 p.s.i. is not present, or the tubing back pressure of about 420 p.s.i. is not present (which pressures may be at or near the design optimum for the tubing annulus sizes and the distance of oil movement to the surface) the valve does not open. Rather the valve awaits further buildup of either annulus or tubing pressure or both before it opens. But unless the system design is badly off, the spread added by the detent, assures enough gas energy for the requisite lift when the valve does open.

Consider now the pressure differential controlled embodiment, in a case wherein something less than 700 annulus p.s.i. is adequate for the lift.

The annulus pressure is controlled to, let us say, about 700 maximum for normal operation. The bellows 39 responds to annulus pressures to move the valve carrier from the FIG. position to the FIG. 6 cocked position, at shall we say, 660 annulus p.s.i. When the valve spring 46 is fully extended as at' the commencement of its compression, it presents relatively low opposition to valve carrier movement away from the valve seat to the cocked position of FIG. 6; and when the detents 56 reach the edge of the recess 55, the detent force into recess 55 aids that portion of the cocking movement occuring when the valve spring 46 is partly compressed and hence is opposing movement with a larger force.

The annulus pressure may go higher to 700 p.s.i., but the valve remains cocked in the position of FIG. 6, waiting until a designed slug of oil has generated a designed amount of tubing back pressure upon the valve closure member 38. When the designed back pressure of perhaps 420 p.s.i. by way of example, has been impressed upon the valve closure member 38, that pressure coupled with the cock-force of the valve spring 46 which may be 75 p.s.i. for example, combines to open the valve.

The valve is seen to be unconcerned about mold excesses above 660 p.s.i. in annulus pressure-it does not open prematurely prior to arrival of the pre-designed sizeable slug of oil to lift. The valve also does not open if annulus pressure is for some reason less than adequate to cock the valve spring 46 and hence inadequate for the lift. The valve functions only within relatively narrowly defined limits of relative high efficiency of oil produced per unit of gas energy consumed.

In normal operation of this embodiment, the valve closure member 38 opens with the detents 56 still in the recess 55, and the valve does not reach the position of FIG. 7. However, should any special circumstance obtain wherein it is desired to open the valve in the absence of effective tubing back pressure, such opening can be obtained (without pulling the string the producing conduit 20. The bellows 39 expands, moving or tending to move the valve carrier 45 toward the valve seat 31. As annulus pressure passes below the nondetained closing pressure of 600 p.s.i. (82 in FIG. 14), the valve carrier 45 is restrained by the detents 56, in the position of FIG. 6 but with the valve closure member 38 held open by the valve spring 46.

But when the detent force, equivalent to perhaps 75 p.s.i. of

annulus pressure, is overcome by the bellows expansion force as at point 83 in FIG. 14, the valve carrier moves toward seat 31 and the valve closure member 38 snaps closed.

In the snap acting valve example of FIG. 14, the 600 p.s.i. annulus pressure line 84 is seen to represent the non-detained closure; the 525 p.s.i. annulus pressure line 85 is the indicator of the detained closure, and the distance 86 between points 82 and 83 is the spread added on closure, by the detent means. The spread added upon opening of such as the snap acting embodiment, is represented by the line 87, the distance between points 77 and 81. The natural valve spread without detents is represented by the line 88, the distance between points 77 and 82. The total spread of a snap acting embodiment is represented by the distance between points 81 and 83, the sum of the spread added on opening 87, the natural spread and the spread 88, and the spread added on closing 86. The pressure differential controlled embodiment perchance may not have the precise 75 p.s.i. spread added on opening that is added by a given detent spring 57 on closing. In this embodiment the detent arrangement as in FIGS. 5-7, affords an increased independence of annulus pressure on opening as well as a controlled and increased spread.

One significant feature of the form of detent means that is here disclosed and obvious equivalents thereof, is that the spread of the valve can be adjusted in the field, by'the mere selection of one from perhaps ten graduated detent springs to be inserted into the valve carrier 45. Nothing need be done at the factory. Simply breaking the threaded joint 61 between housing and mandrel (See FIG. 3), removing the housing, substituting the desired detent spring 57 from a kit of alternatives, and reassembling threaded joint 61, accomplishes in seconds an adjustment of spread of the valve to any desired level.

The Embodiment of FIGS. 8-13 The embodiment of FIGS. 8, 9 and 10, is similar to that of FIGS. 5, 6 and 7, excepting that there is no detention on valve opening, the detention being only on valve closing. Thus, in lieu of the two-sided recess 55 of the embodiment of FIGS. 5, 6 and 7, there is in FIGS. 8, 9 and 10 on the internal surface of the housing 32, a detent shoulder 64 facing away from the valve seat 31.

In FIGS. 11, 12 and 13 there is illustrated a valve mechanism utilizing no detention on valve closing though retaining the detention on valve opening, thereby to increase valve spread and inhibit inadvertent valve opening of upper valves. Thus in lieu of the two sided recess 55 of the embodiment of FIGS. 5, 6 and 7, in FIGS. 11, 12 and 13 there is inside the housing 32 a detent shoulder 63 facing toward the valve seat 31.

The valve, in normal closed position, is illustrated in FIG. 11, where the detent 56 is fully extended when the valve carrier is at its uppermost limit of travel. As gas injection conduit pressure increases and commences the collapse of the bellows, the valve actuator (bellows head 40 and valve carrier 45) commence their movement away from valve seat 31 without restriction by the detent member 56 until the valve spring 46 has been cocked to its design amount, and at that same time the detent member 56 engages the detents shoulder 63.

If the valve is designed for normal opening by the combination of production tubing back pressure and valve spring 46, without further bellows collapse, the normal function of the detents engagement with the detent shoulder 63 is to prevent further bellows collapse, holding the valve in readiness to be opened by rising head in the production tubing. Only in a special situation wherein overriding gas injection pressure is used, or upon original installation in a well full of heavy kill fluid, for two examples, does the detent 56 release and permit the intermediate shoulder 50 to engage the valve closure head 38B and force the valve open.

If the valve is designed for nonnal snap action opening only upon high gas injection pressure and with relative independence of the back pressure from the production tubing, then the effective area of the bellows 39 is made large relative to the cross sectional area of the valve seat 31 and the valve spring 46 is selected to be very weak. In such arrangement, the valve remains closed as gas injection pressure builds up a large amount, held closed by the detent 56 engagement with detent shoulder 63 until a large gas volume and energy of gas pressure is proximate the valve. Only then does the detent 56 release, causing the valve to snap open primarily in response to gas injection pressure that is now higher upon opening, than if there were no detent. Again in this arrangement, the man in the field, without any machine shop or factory function, can easily adjust the amount of the spread-upon-opening, by selecting from his pocket a stronger or weaker detent spring 57.

Valve variations and detent variations of many forms are familiar to those in the art. For example, while an annular detent shoulder (the two sides of recess 55 and detent shoulders 62 and 63 have been disclosed, it is clear that only the two portions cooperating with the two detent members 56 perform a function; accordingly, a full circle detent abutment two portions of which function and two separate detent abutment portions which cooperate concurrently with the two detent members 56, are one and the same for the purposes of this invention.

Further, some valves are run inside the producing conduit as in the Walton US. Pat. No. 3,213,806 or Traylor U.S. Pat. No. l,902,296 rather than mounted on the outside of the tubing string T and this necessitates many obvious structural modifications but would not necessarily depart from the scope of the present invention. Valves may be turned upside down from the form illustrated, and the resilient means of gravitys pull on weighted valve closure members may be utilized in lieu of the valve spring 46.

Also, applicant has built valves with the detent shoulders inside the dome 34 (FIG. 4) and with cooperating detent members and detent spring carried upon the rod 42, all to perform a function identical with that hereinabove described. Still further, in an embodiment including both upwardly and downwardly facing detent shoulders, as in FIGS. 5, 6 and 7, one shoulder may be cut at perhaps 30 and the other at a different angle like perhaps 60 (FIGS. l5, 16, 17), thereby to afford a different mechanical advantage in the detent function upon opening from that upon closing, and thereby to afford a different spread-added upon opening from the spread-added upon closing. Other variations are apparent to those skilled in the art.

Accordingly, without burdening this description with all such possible variations, the foregoing description is to be understood as illustrative only, and not as any limitation upon the scope of the invention as defined in the following claims.

What is claimed is:

1. In a valve adapted to afford fluid communication between a gas injection conduit in a well and a production conduit in the well whereby liquid is produced from the well by means of gas lift, the valve comprising:

a valve chassis including a valve seat having an outlet port on one side thereof,

said valve chassis being adapted to be mounted with said outlet port in communication with said production conduit and with the other side of said valve seat in fluid communication with said gas injection conduit;

a pressure-charged chamber including a bellows having a movable end, said bellows being exposed on one side thereof to said pressure-charged chamber and on the other side thereof to said gas injection conduit pressure, said bellows being responsive to variations in pressure in said gas injection conduit to generate forces upon its movable end in valve-opening and in valve-closing directions;

valve actuator means secured to said bellows movable end so as, when not detained, to be movable thereby with respect to said valve seat between first and second positions toward and away from said seat;

a valve closure member mounted for movement toward said valve seat to close the valve and for movement away from said valve seat to open the valve, said valve closure member being capable of movements with and in response to movements of said actuator and also capable of movements independently of movements of said actuator; said valve member and valve actuator having cooperating abutments by which expansion of said bellows to bring the valve actuator near to the said first position forces said valve closure member sufficiently close to said valve seat so that it does seat to close the valve; bias means operative between said valve actuator and said valve closure member for biasing said valve closure member in the direction away from said valve seat; positive opening means by which said valve closure member is positively forced off said valve seat upon the event of the substantially full collapse of said bellows and thereby the movement of said valve actuator to said second position; detent means operative between said valve actuator means and said chassis for detaining said actuator against movement in response to forces derived from preselected pressure variations while yielding to valve actuator movement in response to larger forces; said detent means comprising two detent members mounted in one of said chassis or said valve actuator,

and an abutment surface in the other of said chassis or said valve actuator for cooperative engagement with each of said detent members at a location between said first and second positions of said valve actuator.

2. The invention defined in claim 1 wherein said detent means is essentially inoperative to detain a first movement of said valve actuator toward said valve seat from a valve-opened position;

wherein said detent means thereupon becomes operative to detain said actuator until closing forces derived from said bellows response to decreased gas injection conduit pressure, have increased;

and wherein said detent means then releases in response to a preselected increase in such forces to permit a second movement of said valve actuator to a position at which the valve closure member seats to close the valve.

3. The invention defined in claim 1 wherein said detent means is essentially inoperative to detain a first movement of said valve actuator from a valve-closed first position after which first movement said bias means is cocked with a valve-opening force;

wherein said detent means thereupon becomes operative to detain said actuator until valve opening forces derived from pressure conditions have increased;

and wherein said detent means releases in response to substantially preselected increased forces to permit a second movement of said valve actuator to open said valve.

4. The invention defined in claim 1 wherein said detent means is essentially inoperative to detain a first movement of said valve actuator from a valve-closed position during which first movement said bias means is cocked with a valve opening force;

wherein said detent means thereupon becomes operative to detain said actuator against movement in response to increases in gas injection conduit pressure which occur during normal routine valve operation, but remains yieldable to release said actuator in response to gas injection conduit pressure above a preselected norm;

wherein said valve is opened in normal operation by the combined force of said cocked bias means and a reduc tion in pressure differential across said valve closure member without said detent releasing and closes in response to gas injection pressure draw down;

wherein upon increase in gas injection conduit pressure significantly above said preselected norm, said positive opening means becomes operative positively to force said valve closure member off said valve seat upon movement of said valve actuator to said second position.

5. The invention defined in claim 1 wherein said detent means is substantially inoperative to detain a first movement of said valve actuator from a valve-closed first position after which first movement said bias means is cocked with a valve-opening force;

wherein said detent means thereupon becomes operative to detain said actuator until valve-opening forces derived from pressure conditions have increased a substantially preselected amount;

wherein said detent means releases in response to preselected increase in valve opening forces to permit a second movement of said valve actuator;

wherein said detent means is essentially inoperative to detain a first movement of said valve actuator toward said valve seat from a full valve-opened position;

wherein said detent means thereupon becomes operative to detain said actuator until closing forces derived from said bellows response to decreased gas injection conduit pressure have increased a substantially preselected amount;

and wherein said detent means then releases in response to a substantially preselected increase in such forces to permit a second movement of said valve actuator to a position at which the valve closure member seats to close the valve.

6. The invention defined in claim 1 wherein said detent means comprises a single compression detent spring carried in said valve actuator;

a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat;

a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement at a point intermediate its said first and second positions.

7. The invention defined in claim 1 wherein said detent means comprises a single compression detent spring carried in said valve actuator;

a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat;

a first shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement away from said valve seat at a point intermediate its said first and second positions;

a second shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement toward said valve seat at a point intermediate its said first and second positions.

8. The invention defined in claim 2 wherein said detent means comprises a single compression detent spring carried in said valve actuator;

a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat;

a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement in the direction toward said valve seat at a point intermediate its said first and second positions.

9. The invention defined in claim 3 wherein said detent means comprises a single compression detent spring carried in said valve actuator;

a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat;

a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement in the direction away from said valve seat at a point intermediate its said first and second positions.

10. The invention defined in claim 5 wherein said detent means comprises a single compression detent spring carried in said valve actuator;

a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat;

a first shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement away from said valve seat at a point intermediate its said first and second positions;

a second shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement toward said valve seat at a point intermediate its said first and second positions.

11. In a valve adapted to afford fluid communication between a gas injection conduit in a well and a production conduit in the well whereby liquid is produced from the well by means of gas lift, the valve combination comprising:

a valve chassis including a valve seat defining an outlet port on one side thereof, said valve chassis being adapted to be mounted with said outlet port in communication with said production conduit and with the other side of said valve seat in fluid communication with said gas injection conduit;

a pressure responsive means mounted upon said chassis and responsive to variations in pressure in said gas injection conduit to generate forces in valve-opening and valveclosing directions;

a valve actuator secured to said pressure responsive means so as, when not detained, to be movable thereby with respect to said valve seat between first and second positions toward and away from said seat;

a valve closure member mounted for movement toward said valve seat to close the valve and for movement away from said valve seat to open the valve, said valve closure member being capable of movements with and in response to movements of said actuator and also capable of movements independently of movements of said actuator;

means for biasing said valve closure member in the direction away from said valve seat;

detent means operative between said valve actuator means and said chassis for releasably holding said actuator against movement in response to preselected pressure variations in said gas injection conduit, said detent means becoming operative at a point intermediate said first and second positions of movements of said actuator means to restrain said actuator against movement during a predetermined change in pressure in said gas injection conduit.

12. The valve defined in claim 11 wherein said detent means comprises:

a single compression detent spring carried by said valve actuator;

a detent member at each end of said detent spring and biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat;

a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said actuator against movement away from said valve seat at a point intermediate its said first and second positions.

13. The valve defined in claim 11 characterized by said detent means comprising:

a first detent shoulder portion facing at least partly toward said valve seat;

a second detent shoulder portion facing at least partly away from said valve seat;

at least one detent member adapted to engage each of said detent shoulder portions;

a spring of strength preselected to urge said detent into engagement with said shoulders and to yield said detent to pass said shoulders upon the development of a preselected force derived from the gas injection conduit pressure.

14. The valve defined in claim 11 characterized by said detent means comprising:

a detent shoulder portion facing at least partly toward said valve seat;

at least one detent member adapted to engage said detent shoulder when said actuator is at a position intermediate its said first and second positions;

a spring of strength preselected to urge said detent into engagement with said shoulder to restrain movement of said actuator during selected changes in pressure conditions and to yield said detent member to pass said shoulder upon the development of a preselected change in gas pressure conditions.

15. The valve defined in claim 11 characterized by said detent means comprising:

a detent shoulder portion facing at least partly away from said valve seat;

at least one detent member adapted to engage said detent shoulder when said actuator is in a position intermediate its said first and second positions;

a spring of strength preselected to urge said detent into engagement with said shoulder to restrain movement of said actuator during selected changes in pressure conditions and to yield said detent member to pass said shoulder upon the development of a preselected change in gas pressure conditions.

16. In a valve adapted to afford fluid communication between a gas injection conduit in a well and a production conduit in the well whereby liquid is produced from the well by means of gas lift, the valve combination comprising:

a valve chassis including a valve seat defining an outlet port on one side thereof, said valve chassis being adapted to be mounted with said outlet port in communication with said production conduit and with the other side of said valve seat in fluid communication with said gas injection conduit',

a pressure responsive means mounted upon said chassis and responsive to variations in pressure in said gas injection conduit to generate forces in valve-opening and valveclosing directions;

a valve actuator secured to said pressure responsive means so as, when not detained, to be movable thereby with respect to said valve seat between first and second positions toward and away from said seat;

a valve closure member mounted for movement toward said valve seat to close the valve and for movement away from said valve seat to open the valve,

a single compression detent spring carried by said valve actuator;

a wedge member movably disposed within said valve actuator and being biased by said compression spring;

a plurality of detent members being engaged by said wedge member and biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said actuator against movement away from said valve seat at a point intermediate its said first and second positions;

said detent members being operative between said valve actuator means and said chassis for releasably holding said actuator against movement in response to preselected pressure variations in said gas injection conduit;

said detent means becoming operative at a point intermediate said first and second positions of movement of said actuator means to restrain said actuator against movement during a predetermined change in pressure in said gas injection conduit, said shoulder portion comprising upwardly and downwardly facing shoulders defined by said chassis, said shoulders being of different angles;

said detent members having different mechanical advantage with one of said shoulders as compared with the mechanical advantage of said detents with the other of said shoulders,

said value closure members being capable of movements with and in response to movements of said actuator and also capable of movements independently of movements of said actuator;

means for biasing said valve closure member in the direction away from said valve seat. 

1. In a valve adapted to afford fluid communication between a gas injection conduit in a well and a production conduit in the well whereby liquid is produced from the well by means of gas lift, the valve comprising: a valve chassis including a valve seat having an outlet port on one side thereof, said valve chassis being adapted to be mounted with said outlet port in communication with said production conduit and with the other side of said valve seat in fluid communicAtion with said gas injection conduit; a pressure-charged chamber including a bellows having a movable end, said bellows being exposed on one side thereof to said pressure-charged chamber and on the other side thereof to said gas injection conduit pressure, said bellows being responsive to variations in pressure in said gas injection conduit to generate forces upon its movable end in valve-opening and in valve-closing directions; valve actuator means secured to said bellows'' movable end so as, when not detained, to be movable thereby with respect to said valve seat between first and second positions toward and away from said seat; a valve closure member mounted for movement toward said valve seat to close the valve and for movement away from said valve seat to open the valve, said valve closure member being capable of movements with and in response to movements of said actuator and also capable of movements independently of movements of said actuator; said valve member and valve actuator having cooperating abutments by which expansion of said bellows to bring the valve actuator near to the said first position forces said valve closure member sufficiently close to said valve seat so that it does seat to close the valve; bias means operative between said valve actuator and said valve closure member for biasing said valve closure member in the direction away from said valve seat; positive opening means by which said valve closure member is positively forced off said valve seat upon the event of the substantially full collapse of said bellows and thereby the movement of said valve actuator to said second position; detent means operative between said valve actuator means and said chassis for detaining said actuator against movement in response to forces derived from preselected pressure variations while yielding to valve actuator movement in response to larger forces; said detent means comprising two detent members mounted in one of said chassis or said valve actuator, and an abutment surface in the other of said chassis or said valve actuator for cooperative engagement with each of said detent members at a location between said first and second positions of said valve actuator.
 2. The invention defined in claim 1 wherein said detent means is essentially inoperative to detain a first movement of said valve actuator toward said valve seat from a valve-opened position; wherein said detent means thereupon becomes operative to detain said actuator until closing forces derived from said bellows'' response to decreased gas injection conduit pressure, have increased; and wherein said detent means then releases in response to a preselected increase in such forces to permit a second movement of said valve actuator to a position at which the valve closure member seats to close the valve.
 3. The invention defined in claim 1 wherein said detent means is essentially inoperative to detain a first movement of said valve actuator from a valve-closed first position after which first movement said bias means is cocked with a valve-opening force; wherein said detent means thereupon becomes operative to detain said actuator until valve opening forces derived from pressure conditions have increased; and wherein said detent means releases in response to substantially preselected increased forces to permit a second movement of said valve actuator to open said valve.
 4. The invention defined in claim 1 wherein said detent means is essentially inoperative to detain a first movement of said valve actuator from a valve-closed position during which first movement said bias means is cocked with a valve-opening force; wherein said detent means thereupon becomes operative to detain said actuator against movement in response to increases in gas injection conduit pressure which occur during normal routine valve operation, but remains yieldable to release said actuator in response to gas injection cOnduit pressure above a preselected norm; wherein said valve is opened in normal operation by the combined force of said cocked bias means and a reduction in pressure differential across said valve closure member without said detent releasing and closes in response to gas injection pressure draw down; wherein upon increase in gas injection conduit pressure significantly above said preselected norm, said positive opening means becomes operative positively to force said valve closure member off said valve seat upon movement of said valve actuator to said second position.
 5. The invention defined in claim 1 wherein said detent means is substantially inoperative to detain a first movement of said valve actuator from a valve-closed first position after which first movement said bias means is cocked with a valve-opening force; wherein said detent means thereupon becomes operative to detain said actuator until valve-opening forces derived from pressure conditions have increased a substantially preselected amount; wherein said detent means releases in response to preselected increase in valve opening forces to permit a second movement of said valve actuator; wherein said detent means is essentially inoperative to detain a first movement of said valve actuator toward said valve seat from a full valve-opened position; wherein said detent means thereupon becomes operative to detain said actuator until closing forces derived from said bellows'' response to decreased gas injection conduit pressure have increased a substantially preselected amount; and wherein said detent means then releases in response to a substantially preselected increase in such forces to permit a second movement of said valve actuator to a position at which the valve closure member seats to close the valve.
 6. The invention defined in claim 1 wherein said detent means comprises a single compression detent spring carried in said valve actuator; a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement at a point intermediate its said first and second positions.
 7. The invention defined in claim 1 wherein said detent means comprises a single compression detent spring carried in said valve actuator; a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a first shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement away from said valve seat at a point intermediate its said first and second positions; a second shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement toward said valve seat at a point intermediate its said first and second positions.
 8. The invention defined in claim 2 wherein said detent means comprises a single compression detent spring carried in said valve actuator; a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement in the direction toward said valve seat at a point intermediate its said first and second positions.
 9. The invention defined in claim 3 wherein said detent means comprises a single compression detent spring carried in said valve actuator; a detent member at each end of said detent spring and thereby biased outwardly froM the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement in the direction away from said valve seat at a point intermediate its said first and second positions.
 10. The invention defined in claim 5 wherein said detent means comprises a single compression detent spring carried in said valve actuator; a detent member at each end of said detent spring and thereby biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a first shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement away from said valve seat at a point intermediate its said first and second positions; a second shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said valve actuator against movement toward said valve seat at a point intermediate its said first and second positions.
 11. In a valve adapted to afford fluid communication between a gas injection conduit in a well and a production conduit in the well whereby liquid is produced from the well by means of gas lift, the valve combination comprising: a valve chassis including a valve seat defining an outlet port on one side thereof, said valve chassis being adapted to be mounted with said outlet port in communication with said production conduit and with the other side of said valve seat in fluid communication with said gas injection conduit; a pressure responsive means mounted upon said chassis and responsive to variations in pressure in said gas injection conduit to generate forces in valve-opening and valve-closing directions; a valve actuator secured to said pressure responsive means so as, when not detained, to be movable thereby with respect to said valve seat between first and second positions toward and away from said seat; a valve closure member mounted for movement toward said valve seat to close the valve and for movement away from said valve seat to open the valve, said valve closure member being capable of movements with and in response to movements of said actuator and also capable of movements independently of movements of said actuator; means for biasing said valve closure member in the direction away from said valve seat; detent means operative between said valve actuator means and said chassis for releasably holding said actuator against movement in response to preselected pressure variations in said gas injection conduit, said detent means becoming operative at a point intermediate said first and second positions of movements of said actuator means to restrain said actuator against movement during a predetermined change in pressure in said gas injection conduit.
 12. The valve defined in claim 11 wherein said detent means comprises: a single compression detent spring carried by said valve actuator; a detent member at each end of said detent spring and biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said actuator against movement away from said valve seat at a point intermediate its said first and second positions.
 13. The valve defined in claim 11 characterized by said detent means comprising: a first detent shoulder portion facing at least partly toward said valve seat; a second detent shoulder portion facing at least partly away from said valve seat; at least one detent member adapted to engage each of said detent shoulder portions; a spring of strength preselected to urge said detent into engagement with said shoulders and to yield said detent to pAss said shoulders upon the development of a preselected force derived from the gas injection conduit pressure.
 14. The valve defined in claim 11 characterized by said detent means comprising: a detent shoulder portion facing at least partly toward said valve seat; at least one detent member adapted to engage said detent shoulder when said actuator is at a position intermediate its said first and second positions; a spring of strength preselected to urge said detent into engagement with said shoulder to restrain movement of said actuator during selected changes in pressure conditions and to yield said detent member to pass said shoulder upon the development of a preselected change in gas pressure conditions.
 15. The valve defined in claim 11 characterized by said detent means comprising: a detent shoulder portion facing at least partly away from said valve seat; at least one detent member adapted to engage said detent shoulder when said actuator is in a position intermediate its said first and second positions; a spring of strength preselected to urge said detent into engagement with said shoulder to restrain movement of said actuator during selected changes in pressure conditions and to yield said detent member to pass said shoulder upon the development of a preselected change in gas pressure conditions.
 16. In a valve adapted to afford fluid communication between a gas injection conduit in a well and a production conduit in the well whereby liquid is produced from the well by means of gas lift, the valve combination comprising: a valve chassis including a valve seat defining an outlet port on one side thereof, said valve chassis being adapted to be mounted with said outlet port in communication with said production conduit and with the other side of said valve seat in fluid communication with said gas injection conduit; a pressure responsive means mounted upon said chassis and responsive to variations in pressure in said gas injection conduit to generate forces in valve-opening and valve-closing directions; a valve actuator secured to said pressure responsive means so as, when not detained, to be movable thereby with respect to said valve seat between first and second positions toward and away from said seat; a valve closure member mounted for movement toward said valve seat to close the valve and for movement away from said valve seat to open the valve, a single compression detent spring carried by said valve actuator; a wedge member movably disposed within said valve actuator and being biased by said compression spring; a plurality of detent members being engaged by said wedge member and biased outwardly from the center axis of movement of said valve actuator in its movements toward and away from said valve seat; a shoulder portion in said chassis for cooperation with each of said detent members to releasably detain said actuator against movement away from said valve seat at a point intermediate its said first and second positions; said detent members being operative between said valve actuator means and said chassis for releasably holding said actuator against movement in response to preselected pressure variations in said gas injection conduit; said detent means becoming operative at a point intermediate said first and second positions of movement of said actuator means to restrain said actuator against movement during a predetermined change in pressure in said gas injection conduit, said shoulder portion comprising upwardly and downwardly facing shoulders defined by said chassis, said shoulders being of different angles; said detent members having different mechanical advantage with one of said shoulders as compared with the mechanical advantage of said detents with the other of said shoulders, said value closure members being capable of movements with and in response to movements of said actuator and also capable of movements independently of movements of said acTuator; means for biasing said valve closure member in the direction away from said valve seat. 